Time division multiplex communication system



April 11, 1961 Filed Aug. '31, 1959 LONG DISTANCE SWITCHING CENTER B. BRIGHTMAN.

LONG

DISTANCE LOCAL OFFICE LONG DISTANCE SWITCHING CENTER LOCAL OFFICE FIG.1

LOCAL OFFICE LOCAL OFFICE SWITCHING CENTER LOCAL OFFICE LOCAL OFFICE INVENTOR.

BARRIE BRIGHTMAN BY FQKM ATTORNEY April 11, 1961 Filed Aug. 31, 1959 REC.

SEND

REC.

SEND

REC.

SEND

REC.

SEND

FIG.2A

B. BRIGHTMAN TIME DIVISION MULTIPLEX COMMUNICATION SYSTEM 18 Sheets-Sheet 2 3| GISILHIOKC) GROUPI LINE SUB-GRI LINE I TERMINATING GISILIO I D'STRIBUTOR UNIT A /34 ASSIGNED TIME Pos.I CLAMP FIG. I9A GROUP I A SUBGROUPI I REC. GATE T I FIG. I9A L. 27b 1/22 GROUPI SUBGROUPI LINE SEND GATE TERMINATING /35 aFlLTER UNIT FIG. l9A ASSIGNED AMP TIME POS. I8l FIG. 9A

eIsI (IooKc GISIO GROUPI su BGROUP Io DISTRIBUTOR TER lIlml ATlNG G2Sl (IOOKC) UNIT ASSIGNED T TIME Pos. I9 I 623w GROUP l l SUBGROUPIO I I REC.GATE l l l I f i /24 GROUPI SUBGROUPIO LINE -SEND GATE TERMINATING & FILTER UNIT ASSIGNED CLAMP TIME POS. I99 7 April 11, 1961 B. BRIGHTMAN TIME DIVISION MULTIPLEX COMMUNICATION SYSTEM Filed Aug. 31, 1959 18 Sheets-Sheet 3 GROUP Raw CLAMP 260 I GROUP SEND GROUPI REc. GATE FIG. I9B

TIME POSITION L PULSE 26b COMMUTATOR GROUP 1 o SEND GATE 28 "a FIG. I98 &

2MC I J U L SEIZE &

DETECTOR 1- GROUP i SUBGROUP DISTRIBUTOR H i 8 3 m a: a: Q D D 29 as a GID(IMC) FL GROUP DIRECT DIALING PULSE REGISTER 62D COMMUTATOR ALLOTTER 8 2 GROUP 2 Q Q Q o i SUBGROUP DISTRIBUTOR 4| GROUP 2 R l N E l kfigN REC. GATE TSP-1 CIRCUIT Tsp o GROUP 2 jD-SEND GATE FIG.2B

April 11, 1961 B. BRIGHTMAN 2,979,570

TIME DIVISION MULTIPLEX COMMUNICATION SYSTEM Filed Aug. 31, 1959 18 Sheets-Sheet 4 ROUTE DIRECT DIALING SELECTOR REGISTER READ OFF CIRCUIT FIG. 23

FIG, 2C REGISTER FINDER RINGING TONE GEN. FIG. 22

BUSY

TONE GEN. FIG. 22

RELEASE TONE GEN. FIG. 22

18 Sheets-Sheet 5 LINK FIG.I9C

LINK ALLOTTER B. BRIGHTMAN CLAMP CONNECTOR RECEIVE TIME DIVISION MULTIPLEX COMMUNICATION SYSTEM SEND FIG. I9B

FIG. I95

6 8 R B R 3 S S S T T T I 2% n 1 9 2 2 3 r n 3 n n w 13 w SEX R 2 oimk 2 c m oiwu om; M F om; 4-1 8 u I E E d m M R R 5 5 R n m M am n a U 4 A C U 4 C 2 .Ir E C 2 m s E T m a F F REC. GATE SEND GATE RING TRIP DETECTOR April 11, 1961 Filed Aug. 31, 1959 FIG.2D

Aprll 11, 1961 B. BRIGHTMAN 2,979,570

TIME DIVISION MULTIPLEX COMMUNICATION SYSTEM Filed Aug. 31, 1959 18 Sheets-Sheet 6 AUDIO AMPLIFIER AUA AUA A F +l2 +l2 l2 F F|G.3A FIG.3B

BLOCKING OSCILLATOR GATE- BOG BOG C BLK.O$C. -|2 B A GATE c 0 i FIG.4A FIG.4B

EMITTER FOLLOWER-EFB EMITTER FOLLOWER-EFE EFB 2 EFE oA B A B B A B i c F|G.5A F|G.5B FIG.6A PIC-3.68

EMITTER FOLLOWER-EFJ EFJ FIG.7A FIG.7B

April 1961 B. BRIGHTMAN 2,979,570

TIME DIVISION MULTIPLEX COMMUNICATION SYSTEM Filed Aug. 51, 1959 18 Sheets-Sheet 8 HIGH SPEED INVERTER-ING INVERTER-INS |2 ING 5 INS B A A B U FIG.I4A FIG.I4B FIG.I5A

INVERTER-INU INU A B I FIG.I6A FIG.I6B

MONOSTABLE MULTlVlBRATOR-MAA MAA I00 MS LOW PASS FILTER-FLN I CC FIG. I8A FIG. I8B

TO LINK ALLOTTER TO ROUTE SEL.

A ril 11, 1961 B. BRIGHTMAN 2,979,570

TIME DIVISION MULTIPLEX COMMUNICATION SYSTEM Filed Aug. 31, 1959 18 Sheets-Sheet 12 GGA YMI-I Ti. GJD INA 2002 LF A/IB IL \I INS GGA GJD 1NA INS A B A B A A wRo [W 2006 2001 GJD INA GJ/D MB A B A B A% c \I D B 2009 200a c l E 208 GJD 2oo| l B FIA T INC B can B GGA INU A B A B FIA 20m FIG. 20

LINK CIRCUIT April 11, 1961 B. 'BRIGHTMAN 2,979,570

TIME DIVISION MULTIPLEX COMMUNICATION SYSTEM Filed Aug. 31, 1959 18 Sheets-Sheet 15 /2IOI SET T IIG E STZT CLAMP B STORAGE BUSY B TO ROUTE sEL. -RESET COUNTER PULSE A 5T SEIZE DET.

OUT 0 1; a TIME 2l03 RELEASE DET. TEST BUSY PULSE ouT B GGA csP-o O A csP-L TIME SLOT PULSE C TSP O REGENERATION ccT. 2IO5 To UNE /2\02 GGA coNNEcToR A TsP-L CALLED TIME sLoT C U CLAMP B sToRAGE BUSY REsET COUNTER PULSE OUT TIME TEST BUSY PULSE I OUT GJD A 2IO4 MAA o GJD 2 SEC. B

7 To RELEASE TONE GEN.

T0 RING TONE GEN. a RING TRIP DET.

To BUSY ToNE GEN.

EFE

I- 2 II I FIG.2I I 0 TO RING T0 RELEAsE LINK CIRCUIT TRIP DET. DET.

April 11, 1961 B. BRIGHTMAN 2,979,570

TIME DIVISION MULTIPLEX COMMUNICATION SYSTEM Filed Aug. 31, 1959 18 Sheets-Sheet 15 TO READ OFF CCT.

a c GGA r 3 24l0 1 24H FLN BOG I i I B A B BLK.OSC. I LPF GATE l I I c o I I l I 24o-r l 2402 TIME I PULSE+| l SET OUT I T REsET COUNTER PULSE I DE ouT I TIME I I PULSE l I OUT I l l I I l I l l I I I l l I I l I I I TO LINK CCTS.

FIG. 24

DETECTOR cIRcuIT (RING TRIP OR RELEASE) April 11, 1961 B. BRIGHTMAN TIME DIVISION MULTIPLEX COMMUNICATION SYSTEM 18 Sheets-Sheet 16 Filed Aug. 31, 1959 llllllllllllllllllllllllllllllllll |o||l|| l F0] 3 M u G A D M MU T llllllllllllllllllllllllllllllllllll I|| 0 T|o o1 2 M s G 3 0 A C D E J I B G w /k 2 A 52.1 mo 21 llL 0 TO LINK CCTS.

FIG

TPI99 TP19O TPIBO TPIBI April 11, 1961 B. BRIGHTMAN 2,

TIME DIVISION MULTIPLEX COMMUNICATION SYSTEM Filed Aug. 31, 1959 18 Sheets-Sheet 17 U U [Ll LJ J [J Li LT F1] I! I1 mjj 1 :ll: FL: L FE|;L'1F} mwww g April 1961 B. BRIGHTMAN 2,979,570

TIME DIVISION MULTIPLEX COMMUNICATION SYSTEM Filed Aug. 31, 1959 18 Sheets-Sheet 18 TP2O TPIO

TP2OO TPl TF2 TF3 TIME DIVISION MULTIPLEX COMNIUNICATION SYSTEM Rochester, N.Y., assignor to General Dynamics Corporation, Rochester, N.Y., a corporation of Delaware Barrie Brightman,

Filed Aug. 31, 1959, Ser. No. 837,061

15 Claims. (Cl. 179'-15) by transmission networks, or highways, of the time posi-' tion channel type. In the system disclosed in the aboveidentified copending application, each of the transmission networks comprises thirty-two time position channels and an individual channel is permanently assigned to each line of the system. Connections are completed between calling and called lines, which may have time positions on the same or different transmission networks assigned thereto, by link circuits common to the lines of the system. Each link circuit comprises a relay per transmission network for controlling connection to the transmission network assigned to the calling line and a relay per transmission network for controlling connection to the transmission network assigned to the called line in addition to calling and called gates for controlling con nection to the time position channels assigned to the calling and called lines, respectively.

It is, of course, desirable to reduce the number of transmission networks required for a giyen number of lines so as to reduce the amount of equipment required to establish connections between the lines. The only way that this can be accomplished as a practical matter is to increase the channel capacity of each transmission network by reducing the width of each channel since the duration of each channel frame is controlled by the fact that each line must be sampled at 8 kc. or greater for accurate reproduction of the sampled signals. In the system disclosed in the above-identified application, each channel is 1.25 microseconds in width and a guardtime of 1.25 microseconds is provided between channels so that the master oscillator, which controls the development of the time position defining pulses, must have a frequency of 400 kc. Now, if the channel capacity of each transmission network is increased to 200, for example, each channel is .25 microsecond in width, and the guard time between channels is .25 microsecond in width, the master oscillator must have a frequency of two megacycles. When frequencies and pulse widths of the latter order are used, the wire length and the stray capacitance in the wiring required to distribute the pulses to the units terminating the lines become extremely critical because of the nonuniform pulse delays introduced throughout the system.

Accordingly, it is the general object of this invention to provide a new and improved, communication system the time division multiplex type.

It is a more particular object of this invention to provide a new and improved communication system of the time division multiplex type having increased channel capacity over systems of the prior art.

.Briefly, the present invention accomplishes the-above FPICC the system are divided into groups and subgroups with a line gate, a subgroup gate, a group gate, and a master gate being interposed in anindividual connection between each line and the transmission network. The master gate is operated during each time position channel, the group gates are operated in succession during succeeding operations of the master gate, the subgroup gates for each group of lines are operated at a submultiple of the frequency of operation of the group gate for that. group of lines, and the line gates for each subgroup of lines are operated at a submultiple of the frequency of operation of the subgroup gate for that subgroup of lines.

Thus, the channels of said network are assigned succes-- sively to the groups of lines, the channels assigned to each group of lines are assigned successively to the subgroups of lines in that group of lines, and the channel's assigned to each subgroup of lines are assigned successively to the lines in that subgroup of lines.

Particular advantages of the above-described grouping method are realized when the system is of the resonant transfer type, as illustrated. First, a common send low-pass filter can be provided for each subgroup of lines since the lines of each subgroup are connected in turn to the filter for that subgroup of lines with one line being connected during the period of time between successive operations of the subgroup gate for that subgroup of lines, and, second, the master gate can be controlled to have a shorter operated time than any of the other gates and thus be the only gate in the system which has a precise requirement as to operated time since it controls the time interval during which energy is transferred between a line and the transmission network.

Further objects and advantages of the invention will become apparent as the following description proceeds, and features of novelty which characterize the invention will be pointed out in particularity in the claims annexed to and forming a part of this specification.

For a better understanding of the invention, reference may be had to the accompanying drawings which comprise twenty-seven figures on eighteen sheets.

Fig. 1 shows the trunking diagram of the disclosed telephone system,

Figs. 2A-2D, when arranged in order from left to right, show a long distance switching center in block diagram form,

Figs. 3A-18B show the logic symbols, together with a typical circuit represented by each symbol, which are used throughout the detailed circuit drawings,

Figs. l9A-l9C, when arranged in order from left to right, show the voice path or communication connection between the lines and the transmission network of a long distance switching center,

Figs. 20 and 21, when arranged with Fig. 21 to the right of Fig. 20, show a link circuit for use in a long distance switching center,

Fig. 22 shows a tone generator for use in a long distance switching center,

Fig. 23 shows a read-off circuit for use in a long distance switching center,

Figs. 24 and 25, when arranged with Fig. 25 to the right of Fig. 24, show a detector circuit for use in a long distance switching center, and

Figs. 26 and 27, when arranged with Fig. 27 to the right of Fig. 26, show graphic illustrations of the pulses used to control the multiplexing in a long distance switching center.

The general operation of the system in which the in-. vention has been disclosed can best be understood by reference toFi'gs. 2A-2D, inclusive, in conjunction with reference to the trunking diagram shown in Fig; 1. The" block diagram of Figs. 2A-2D represents a part of the equipment comprising each of thelong distance, switching centers 2, 5 and 8 of Fig. 1. Details of theequipmerit comprising each of the local offices of Fig. 1 are disclosed in copending application Serial Number 814,928, filed May 21, 1959, andassigned to the same assignee as the present invention. The lines interconnecting the subscriber stations and the local ofiices and the lines interconnecting the various offices are four-wire and may be either physicalwire or radio links. Further, all signaling in the system is of the voice frequency type.

As shown in Fig. 1, calls between subscribers in different local ofiices may be routed through one or 'more long distance switching centers. For example, a call from subscriber station A in local office 1 to subscriber station B in local oifice. 9is routed through long distance switching centers 2, 5 and 8. The call is initiated by the transmission of a seize signal from station A when the handset at that station is removed from its cradle. Upon receipt of dial tone from local office 1, the transmission of a seize signal by station A is terminated and the subscriber at station A then proceeds to key the routing digits required to select subscriber station B. The keyed number comprises routing digits corresponding to long distance switching centers 2, 5 and 8, an arbitrary digit,

which may be the digit 1, identifying local, the digit corresponding to local ofiice 9, and the three digit directory number of station B in local ofiice 9. The first keyed digit controls the equipment in local ofiice 1 to select an idle trunk line to long distance switching center 2 and to transmit a seize signal over the selected trunk line. In switching center 2, the receipt of a seize signal over a trunk line from a local office controls an idle direct dialing register in that center to connect to the trunk line over which the seize signal is received and the second and all succeeding digits received from station A are stored in the direct dialing register taken into use. The second.

digit is utilized to control common equipment in switching center 2 to select an idle trunk line to switching center 5, the direct dialing register taken into use is then controlled to connect to the selected trunk line and to transmit a seize signal over the trunk line to switching center 5.

In switching center 5, the receipt of a seize signal over a trunk line from another long distance switching center controls an idle incoming register in that switching center' to connect to the trunk line over which the seize signal is received and to transmit a seize acknowledge signal back over that trunk line to the controlling direct dialing regis ter in switching center 2. The incoming register has not been shown in the block diagram of Figs. 2A-2D of this application since it is not necessary to the understanding of the present invention. Upon receipt of the seize acknowledge signal, the controlling direct dialing register terminates the transmission of a seize signal and then transmits the third digit, which corresponds to switching center 8, to the incoming register in switching center 5. The third digit is stored in the incoming register in switching centerS and an acknowledge signal representing that digit is returned to the controlling direct dialing register. The direct dialing register then transmits a second seize signal, incoming register in switching center 5 then controls the common equipment in that oflice to select an idle trunk line to switching center 8, a connection is established between the calling and called trunk lines in switching center 5, and the incoming register in switching center 5 is then released for use on another call. The seize signal transmitted by the controlling direct dialing register, and which controlled the equipment in-switching center 5 to route the call through that center, is then detected in switching center 8 and an idle incoming register in that switching center is connected to the calling trunk line in that switching center. lilieeaction inswitching;

center 8 is identical to that just described in switching center'S 'with theexceptionthatthe first digit 1 trans mitted to switching center 8 controls the incoming register to delay until two digits have been received before switching the call through to an idle trunk line extending to local office 9. Thus, it.,.can beseen that the extension of a call is controlled by thedirect dialing register and the first switching center encountered, the intermediate switching centers are controlled by a single digit to select an idle trunk line to .the next switching center, and the final long distance switching center is controlled by two digits to select the desired local office. When the seize signal which controls the equipment in switching center 8 to route the call through that center to local otfice 9 is detected in local otfice 9 and a subscriber register is connected to the trunk line over which the seize signal is received, dial tone is returned over the extended connection to the controlling direct dialing register to indicate to said register that the call has progressed to a local office. The controlling direct dialing register is responsive to the receipt ofdial tone to transmit an interlock request signalto local oflice 9 over the extended connection.

The subscriber register in local ofiice 9 is responsive to the receipt of an interlock request signal to transmit a seize acknowledge signal to the controlling direct dialing register, and the three digits of the directory number of station B are then transmitted and acknowledged in turn. At the completion of the transmission of the directory number to local cities 9, an end of call signal is transmitted from office 9 to the controlling direct dialing register regardless of the idle or busy condition of the selected called line. The end of call signal controls the equipment in long distance switching center 2 to connect the calling and called trunk lines in that ofiicetogether and the direct dialing register used on the call is then released from the connection and freed for use on another call. A connectionis now completed between station A and local ofiice 9 sothat the ringback tone, or busy tone, transmitted from ofiice 9 may be heard by the calling subscriber at station A.

Each of the long distance switching centers is also equipped with one or more service lines which may be reached through the .direct dialing register provided in that switching center.

The block diagram. of the long distance switching center, which is shown in Figs. 2A-2D, will now be described in more detail. Although just four line terminating units, namely, units 21-24, have been shown, it is to be understood that there is provided a line terminating unit for each trunk line terminating in the exchange and a line terminating unit for each service line in the exchange;

As illustrated, the line terminating units, the direct dialing registers, the route selector, and the link circuits are interconnected by a highway transmission network of the four-wire type which comprises two hundred time division channels. As illustrated, the lines of the system are divided into two one hundred line groups, and the groups of lines are each subdivided into ten ten-line sub groups. For example, illustrated line terminating unit 21 terminates the first line in the first subgroup of the first group, unit 22 terminates the tenth line in that sub group, unit 23 terminates the firstline in the tenth subgroup of the first group, and unit 24 terminates the tenth llne in that subgroup. A master gate, which comprises receive gate 25A and send gate 25B, a group gate such as the. group gate for group 1, which comprises group i receive gate 26A and group 1 send gate 26B, a subgroup gate such as the gate for group 1 subgroup 1, which cornprises group 1 subgroupl receive gate 27A and group 1 subgroup lsend gate and filter 27B, and a line gate, which is included in each line terminating unit, are interposed in an individualconnection' between each line and. the transmission 1 network. Thus, the line; terminated by 

